Wireless communication systems are widely deployed to provide various types of communication content and services such as, e.g., voice content, data content, video content, packet data services, broadcast services, messaging services, multimedia services, and so on. Typical wireless communication systems can be multiple-access systems capable of supporting communication with multiple users by sharing the available system resources (e.g., bandwidth and transmit power). Examples of such multiple-access systems can include frequency division multiple access (FDMA) systems, 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) systems, and orthogonal frequency division multiple access (OFDMA) systems.
Generally, a wireless multiple-access communication system can simultaneously support communication for multiple wireless mobile devices. Each mobile device can communicate with one or more base stations via transmissions on the forward and reverse links. The forward link (or downlink) refers to the communication link from the base stations to the mobile devices, and the reverse link (or uplink) refers to the communication link from the mobile devices to the base stations. This communication link may be established via a single-in-single-out (SISO), multiple-in-signal-out (MISO), or a multiple-in-multiple-out (MIMO) system.
Wireless communication systems typically employ a particular carrier frequency for transmitting information. The carrier frequency chosen can depend on a type of the wireless system. For instance, cellular systems employ government-licensed frequency spectra, whereas other systems (e.g. radio, Wi-Fi, etc.) employ non-licensed spectra. In addition, bandwidth of the carrier frequency is related to an amount of data that can be conveyed in a period of time, also referred to as throughput or data rate.
Although a carrier bandwidth is generally fixed by a particular wireless system (e.g. 2 megahertz (MHz), 2.5 MHz, 5 MHz, and so on), multi-carrier systems have recently been developed to increase bandwidth for applications requiring high data rates. Furthermore, multi-carrier systems can yield improved resource utilization and spectrum efficiency by joint resource allocation and load balancing across the multiple carriers. A multi-carrier system is a system with the capability to transmit information on two or more carrier frequencies. This capability may exist in both downlink and uplink connections; alternatively, a multi-carrier system may have multi-carrier capability only on uplink or only on downlink. In a multi-carrier system, a mobile device can be allocated multiple carrier channels, which are aggregated by the mobile device to increase the rate at which information is transmitted to or from the mobile device. When traffic requirements for the mobile device diminish, the additional carrier(s) can be released, freeing up a channel for other mobile devices.
As an example of the foregoing, multi-carrier high speed packet access (MC-HSPA) is an evolution of the HSPA systems, in which two 5 MHz carrier channels are aggregated to increase channel bandwidth, resulting in increased throughput and data rates. The MC-HSPA system is backward compatible for mobile devices designed with older protocols, such as the 3GPP Release 7 (R7), R6, R5, and Release '99 (R99). In addition, for operators, the MC-HSPA system enables efficient and flexible spectrum asset utilization even if multiple carriers licensed to the operator are not contiguous within the frequency spectrum.